The current invention relates to the field of mechanical couplings. More specifically, the invention relates to an improved flexible coupling system for coupling a shaft of one rotating member to a shaft or flywheel of another rotating member.
Mechanical systems often consist of a number of energy converting devices. A few examples of such devices include engines, motors, pumps, alternators, generators, and turbines. These devices are often physically connected to one another via a mechanical coupling to realize the potential of one energy source by converting it into a more useful form. For example, the rotating shaft of an internal combustion engine may drive a flywheel that is, in turn, coupled to the shaft of a pump or other driven device. The mechanical coupling serves to transfer the kinetic energy generated by the engine to drive the load, particularly by transmitting torque to the load during operation.
A variety of mechanical couplings are known and commercially available for connecting one rotating member to a second rotating member. All of these have limitations that impact the implementation and performance of the coupling when used in a mechanical system. One limitation is that existing couplings have a number of parts that have to be aligned in order to engage the coupling. The interaction and physical configuration of these parts often make them difficult to install and implement, as well as to service. Such difficulties lead to increased installation time and system downtime when servicing is required, particularly when the coupling is used in an application where direct access is limited. In this situation, the user has the difficult task of blindly aligning and engaging these coupling elements.
For example, some couplings require the alignment of a through hole in one element to a threaded hole in a second element in order to engage a fastener. The process of visually aligning these elements becomes tedious and time consuming when visual access to the coupling is limited. Furthermore, the installation task becomes even more difficult when alignment or interaction between more than two coupling elements is required. Thus, there is a need for a coupling that eliminates the alignment requirement between mating coupling elements.
Another limitation is that the couplings can be bulky and require more installation space than is available. In particular, the coupling might require excess installation room for engaging items such as the fasteners discussed above. This excess room is usually referred to as “dead space” and is only required for the initial assembly or disassembly process. Thus, there is a need for a coupling that reduces the required installation dead space.
Furthermore, the radial profile of mechanical couplings can also make installation and servicing difficult. The radial profile is typically driven by the alignment and mechanical interaction of multiple coupling elements as discussed above. For example, a fastener might be used to complete the coupling by loading a face on a first coupling element and engaging a thread in a second coupling element thereby securing the two parts together. The purpose of bringing these two elements together is often to capture a third coupling element therebetween. The mechanism described functions by placing the fastener in tension and requires that the fastener pass through or around the element being captured. Therefore, the coupling is often configured with the captured element and fastener located at different and non-concurrent radial distances from the centerline of the coupling. The end result is an increase in the radial profile to allow for the non-concurrence. Thus, there is a need for a coupling system that does not require the fastening element to pass through the clamped element. This would not only reduce the radial profile of the coupling, but would also allow the coupling to accept larger shaft diameters without requiring more radial space to accommodate the larger shaft diameter.
A further limitation results from the misalignment of the coupled shafts. This misalignment can be both axial (offset centerlines) and angular (non-perpendicular faces or misaligned axes of the driving and driven machines). Practically speaking, this misalignment can never be completely eliminated. Those skilled in the art will appreciate the advantages of a coupling device that could still function even when the shafts or other rotating elements are not in perfect alignment.
Some commercially available couplings address the misalignment issue by implementing a flexible element into the coupling, but often do so at the cost of reduced torque carrying capacity. This limitation may result from not applying the clamping force directly to the outer periphery of the element being captured, or from the forces being unevenly distributed across this periphery. The end result is that the torque carrying capacity of the coupling is reduced because the captured element may tend to peel out of the clamping mechanism. A coupling designed to apply a clamping force to the outer periphery of a captured element and/or evenly distribute forces across this periphery would have particular advantage over current designs.
Another issue arises as a result of dynamic imbalances inherent in any rotating device. At high rotational velocities these imbalances can result in severe lateral, torsional, and axial vibrations that are then transmitted through the system via the coupling. These vibrations cause the system to run less efficiently and can also damage vibration sensitive devices, such as bearings. A coupling that can dampen and isolate vibration, thereby preventing their transmission, would be of particular benefit.
Finally, most commercially available couplings make use of some type of threaded member for securing elements in place. The vibrations discussed above can cause these threaded members to be unthreaded. When this self-loosening occurs, the forces holding the coupling together are no longer present, potentially permitting the coupling to disengage. Thus, there is a need for a coupling that incorporates a positive locking feature to prevent threaded parts from self-loosing.